1. Field of the Invention
This invention relates generally to determining analyte concentrations within living tissue.
2. Description of the Related Art
Millions of diabetics are forced to draw blood on a daily basis to determine their blood glucose levels. A search for a non-invasive methodology to accurately determine blood glucose levels has been substantially expanded in order to alleviate the discomfort of these individuals.
A significant advance in the state of the art of non-invasive blood glucose analysis has been realized by an apparatus taught in U.S. Pat. No. 6,198,949, titled SOLID-STATE NON-INVASIVE INFRARED ABSORPTION SPECTROMETER FOR THE GENERATION AND CAPTURE OF THERMAL GRADIENT SPECTRA FROM LIVING TISSUE, issued Mar. 6, 2001; and by methodology taught in U.S. Pat. No. 6,161,028, titled METHOD FOR DETERMINING ANALYTE CONCENTRATION USING PERIODIC TEMPERATURE MODULATION AND PHASE DETECTION, issued Dec. 19, 2000; and in the Assignee""s U.S. patent application Ser. No. 09/538,164, titled METHOD AND APPARATUS FOR DETERMINING ANALYTE CONCENTRATION USING PHASE AND MAGNITUDE DETECTION OF A RADIATION TRANSFER FUNCTION. Additional information relating to calibration of such non-invasive blood analysis is taught in U.S. Pat. No. 6,049,081, titled SUBSURFACE THERMAL GRADIENT SPECTROMETRY, issued Apr. 11, 2000; and by U.S. Pat. No. 6,196,046 B1, titled DEVICES AND METHODS FOR CALIBRATION OF A THERMAL GRADIENT SPECTROMETER, issued Mar. 6, 2001. The entire disclosure of all of the above mentioned patents and patent applications are hereby incorporated by reference herein and made a part of this specification.
U.S. Pat. No. 6,198,949 discloses a spectrometer for non-invasive measurement of thermal gradient spectra from living tissue. The spectrometer includes an infrared transmissive thermal mass, referred to as a thermal mass window, for inducing a transient temperature gradient in the tissue by means of conductive heat transfer with the tissue, and a cooling system in operative combination with the thermal mass for the cooling thereof. Also provided is an infrared sensor for detecting infrared emissions from the tissue as the transient temperature gradient progresses into the tissue, and for providing output signals proportional to the detected infrared emissions. A data capture system is provided for sampling the output signals received from the infrared sensor as the transient temperature gradient progresses into to the tissue. The transient thermal gradients arising due to the intermittent heating and cooling of the patient""s skin generate thermal spectra which yield very good measurements of the patient""s blood glucose levels.
Although the apparatus taught in the above-mentioned U.S. Pat. No. 6,198,949 has led to a significant advance in the state of the art of non-invasive blood glucose analysis, one possible source of error in such analysis arises due to physiological variation across the patient population. This variation, as well as other factors, can introduce systematic error into the measurements being performed.
In one embodiment, there is provided an adapter for presenting a sample of body fluid including an analyte to a window of a noninvasive analyte detection system. The adapter comprises a base material comprising a first side and a second side, and a sample accommodating volume extending between an opening in the second side of the base material and an opening in the first side of the base material.
In another embodiment, there is provided an adapter for presenting a sample of whole blood including an analyte to a window of a noninvasive analyte detection system. The adapter comprises a base material comprising a first side and a second side, and an optically transparent layer comprising a first side and a second side. The second side of the optically transparent layer is positioned proximate the first side of the base material. The adapter further comprises a sample accommodating volume extending between the second side of the optically transparent layer and an opening in the second side of the base material.
In another embodiment, there is provided an adapter for presenting a sample of whole blood including an analyte to a window of a noninvasive analyte detection system. The adapter comprises a base material comprising a first side having a first opening and a second side having a second opening, and a sample accommodating volume formed in the base material and extending between the first opening and the second opening.
In another embodiment, there is provided a method for calibrating a noninvasive detection unit including a window. The method comprises withdrawing a sample of bodily fluid from a patient, positioning the sample over the window, analyzing the sample with the noninvasive detection unit and generating an invasive-measurement output representing the concentration of an analyte. The method further comprises placing the window in contact with the skin of the patient, analyzing the patient""s tissue with the noninvasive detection unit and generating a noninvasive-measurement output representing the concentration of the analyte. The method further comprises comparing the invasive-measurement output and the noninvasive-measurement output to estimate an error, and correcting the noninvasive-measurement output based on the error.
In another embodiment, there is provided a method for calibrating a noninvasive detection unit including a window. The method comprises determining whether there is a restricted period in effect, selecting an on-site or an alternative site measurement location based on whether a restricted period is in effect, and withdrawing an sample of bodily fluid from a patient at the selected measurement location, wherein the sample comprises at least one analyte. The method further comprises positioning the sample over the window, analyzing the analyte in the sample using the noninvasive detection unit and generating an invasive-measurement output representing a characteristic of the analyte. The method further comprises placing the window of the noninvasive detection unit in contact with the skin of the patient, analyzing the analyte in the tissue of the patient with the noninvasive detection unit, and generating a noninvasive-measurement output representing the characteristic of the analyte. The method further comprises comparing the invasive-measurement Output and the noninvasive-measurement output to estimate an error, and correcting the noninvasive-measurement output based on the error.
All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.